Mtfp1 ablation enhances mitochondrial respiration and protects against hepatic steatosis

Hepatic steatosis is the result of imbalanced nutrient delivery and metabolism in the liver and is the first hallmark of Metabolic dysfunction-associated steatotic liver disease (MASLD). MASLD is the most common chronic liver disease and involves the accumulation of excess lipids in hepatocytes, inflammation, and cancer. Mitochondria play central roles in liver metabolism yet the specific mitochondrial functions causally linked to MASLD remain unclear. Here, we identify Mitochondrial Fission Process 1 protein (MTFP1) as a key regulator of mitochondrial and metabolic activity in the liver. Deletion of Mtfp1 in hepatocytes is physiologically benign in mice yet leads to the upregulation of oxidative phosphorylation (OXPHOS) activity and mitochondrial respiration, independently of mitochondrial biogenesis. Consequently, liver-specific knockout mice are protected against high fat diet-induced steatosis and metabolic dysregulation. Additionally, Mtfp1 deletion inhibits mitochondrial permeability transition pore opening in hepatocytes, conferring protection against apoptotic liver damage in vivo and ex vivo. Our work uncovers additional functions of MTFP1 in the liver, positioning this gene as an unexpected regulator of OXPHOS and a therapeutic candidate for MASLD.

Sample sizes were deemed sufficient, taking into account the literature referencing analogous experiments (Wai et al. Science 2015), as well as the magnitude and consistency of measurable differences between groups, power studies (conducted in partnership with Biostatisticians at the Institut Pasteur), and the available space within animal containment facilities utilized for breeding (BIME) and experimentation (Monod).
No data points were excluded in this study.
Animal experiments were independently repeated a minimum of three times using distinct biological samples.Ex vivo and in vitro experiments, encompassing cell death/growth assays, seahorse measurements, and biochemical assays, were conducted on two or three biologically independent samples, consistently yielding reproducible data.It's noteworthy that all replication attempts were successful, and the corresponding replicates have been incorporated into the figure legends for reference.
In animal studies, both control and mutant mice were randomly assigned to cages and gender-separated upon weaning.Physiological measurements were taken randomly, cage by cage.For pair-wise experimental measurements conducted in vitro (such as Oroboros, hepatocytes isolation, and electro-physiology), mutant and wild type samples were simultaneously measured.In experiments other than animal studies, samples were allocated randomly between genotypes whenever feasible.However, random allocation wasn't possible when dealing with simultaneous, pairwise measurements (e.g., a machine with only two chambers).In such cases, randomly selected wild type control and mutant samples were simultaneously measured in individual chambers.
Blinding was implemented whenever feasible, especially in all animal experiments.However, this practice was not applicable in experiments where the protocols necessitated parallel, pair-wise measurements (as mentioned earlier).In such instances, random wild type and mutant samples were obtained from previously genotyped cells or animals.For cell and tissue image acquisition and analysis, automated processes were employed, ensuring that the experimenter remained blinded to the data.Additionally, all data underwent analysis using unbiased statistical methods.
Source Data are provided with this paper.The datasets generated during the current study are available in the European Nucleotide Archive (NEO) repository and Proteomics Identification Database (PRIDE) (ProteomeXchange Consortium).Accession numbers and the web links are as follows.Bulk RNAseq: (ENA: E-MTAB-12920) (mouse reference genome GRCm39), Liver proteome of mice (PXD041197), and liver interactome data (PXD046262).The total datasets of fluorescence microscopy images generated and analyzed during the current study are not publicly available due to the incompatibility of exporting comprehensible file names linked to cell, treatment, and time identifiers from the Harmony 4.9, Perkin Elmer software but are available from the corresponding author on reasonable request.Note that full information on the approval of the study protocol must also be provided in the manuscript.

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